1. Field of the Invention
The present invention relates to refrigeration systems and, more specifically, to maintaining a relatively constant temperature of refrigerant passing through an evaporator, where the evaporator is exposed to a variable thermal load.
2. Description of the Related Art
In common refrigeration systems that operate at constant evaporating temperature under variable cooling load, the refrigerant is compressed in a variable speed compressor and then cooled in a condenser. After the refrigerant is cooled in the condenser, it is passed through an expansion device, or valve, to lower its pressure. The cooled, low-pressure refrigerant then enters an evaporator where the refrigerant absorbs thermal energy as its phase changes from a liquid to a vapor. Subsequently, the refrigerant in the evaporator is drawn into the compressor and re-cycled through the circuit.
Electronic components, such as microprocessors and laser diodes, perform better and more reliably when they are maintained at a constant, low temperature. Commonly, a refrigeration system is used to cool these electronic components by placing the evaporator near the components to absorb the heat that they produce. The heat produced by and emanating from these components may change over time depending on several factors. In order to maintain these components at a relatively constant temperature, the refrigeration system must be able to increase or decrease its cooling load in response to these changes.
To adjust the cooling load provided by the refrigeration circuit, the compressor may be cycled on and off which essentially starts and stops the working fluid from flowing through the circuit. However, cycling a compressor in this manner creates difficulties in the compressor lubrication system causing premature wear. Further, turning the refrigeration cycle on and off in this manner allows the temperature of the electronic components to fluctuate substantially. These substantial temperature swings may cause soldered connections to break or cause undesired condensation on the components.
Alternatively, variable speed compressors can be used to adjust the flow rate of the working fluid in the circuit to provide a variable, yet continuous, cooling load to the evaporator. However, variable speed compressors emit a variety of frequencies during operation which may cause nearby electronic components to malfunction. Further, variable speed compressors typically require additional electronics and hardware to convert AC power to DC power, thus increasing the cost of the refrigeration system.
What is needed is a refrigeration system which is an improvement over the foregoing.